AUTOMATIC ASSEMBLY SEQUENCES GENERATION BY PATTERN-MATCHING

The problem of automatically finding all the feasible assembly sequences for a set of n parts that construct a mechanical object is presented. A novel method proposed here is feasible and practical in generating all the feasible assembly sequences when the number of parts is greatly increased. Generally, to generate all the assembly sequences, the precedence logical forms are obtained from the answers of relation between a pair of parts (which is called a liaison) consecutively questioned by a design engineer, and the assembly sequences are deduced by logic induction. Previous work has shown that the question-answer pattern requires 2l operations (Here l is total number of the liaisons and bounded between n-1 and (n2-n)/2). An efficient method coupled with a pattern-matching operation to generate all the feasible assembly sequences is proposed. Acquisition of the precedence knowledge is derived from the terminology of the state constrained traveling saleman problem (SCTSP). The SCTSP method is to prohibit generation of next valid states during states expansion. The solution of the assembly schedule can be easily obtained by solving SCTSP as well. This approach results in only l questions to be answered. For a special case with single fixture assembly system, the question-answer format only requires n questions to be answered resulting in reducing the order of complexity. The designed precedence knowledge is able to reduce the complexity of solving the ordering problem both on the procedures of acquisition and generation. The proposed method shows feasibility and economy for a large number of parts to be assembled.